linux-kernel - Re: [PATCH v6 48/76] x86/entry/64: Add entry code for #VC handler

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Message-ID: <20200831173024.GN27517@zn.tnic>
Date:   Mon, 31 Aug 2020 19:30:24 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Joerg Roedel <joro@...tes.org>
Cc:     x86@...nel.org, Joerg Roedel <jroedel@...e.de>, hpa@...or.com,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Martin Radev <martin.b.radev@...il.com>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v6 48/76] x86/entry/64: Add entry code for #VC handler

On Mon, Aug 24, 2020 at 10:54:43AM +0200, Joerg Roedel wrote:
> @@ -674,6 +675,56 @@ asmlinkage __visible noinstr struct pt_regs *sync_regs(struct pt_regs *eregs)
>  	return regs;
>  }
>  
> +#ifdef CONFIG_AMD_MEM_ENCRYPT
> +asmlinkage __visible noinstr struct pt_regs *vc_switch_off_ist(struct pt_regs *eregs)
> +{
> +	unsigned long sp, *stack;
> +	struct stack_info info;
> +	struct pt_regs *regs;
> +
> +	/*
> +	 * In the SYSCALL entry path the RSP value comes from user-space - don't
> +	 * trust it and switch to the current kernel stack
> +	 */
> +	if (eregs->ip >= (unsigned long)entry_SYSCALL_64 &&
> +	    eregs->ip <  (unsigned long)entry_SYSCALL_64_safe_stack) {
> +		sp = this_cpu_read(cpu_current_top_of_stack);
> +		goto sync;
> +	}
> +
> +	/*
> +	 * From here on the the RSP value is trusted - more RSP sanity checks
			^^^^^^^

Fished out one valid warning from the confused blabla checkpatch spits out:

WARNING: Possible repeated word: 'the'
#276: FILE: arch/x86/kernel/traps.c:696:
+        * From here on the the RSP value is trusted - more RSP sanity checks

IOW, as I tell other submitters:

Please integrate scripts/checkpatch.pl into your patch creation
workflow. Some of the warnings/errors *actually* make sense.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette